A conventional abdominal exerciser is shown in FIG. 1. The exerciser comprises an upright metal frame 1 provided on the floor, a pulley 2 on top of the frame 1, a steel rope 3 adapted to run the grooved rim of the pulley 2, a plurality of stacked blocks of weight 4 fastened at one end of the steel rope 3, a lower pulley 5 adjacent the blocks of weight 4, a pulling member 6 coupled to the other end of the steel rope 3 which passes the lower pulley 5, the pulling member 6 having left and right handles 7 adapted to be held by the hands, a pad 8 in the rear of the frame 1, the pad 8 being proximate the floor, and a pedal 9 in the intermediate portion of the frame 1. In use, a person lays his/her buttock on the pad 8 with two legs urged against the pedal 9, the left and right handles 7 held by two hands, and the back moved toward the rear of the frame 1 back and forth. As a result, the blocks of weight 4 are lifted as the other end of the steel rope 3 is pulled rearwardly by pulling the handles 7 to and fro. For lifting the blocks of weight 4 above their original position a predetermined height and maintaining the same for a period of time, the arms and the legs of the person has to exert much force. However, little force is exerted by the abdominal muscles. Hence, the prior abdominal exerciser fails to train the abdomen as it claims. Thus, the need for improvement still exists.